newtype Rule = Rule String deriving (Show)

class RuleSet a where
  getRules :: a -> [Rule]

data Bus = Bus [Rule] deriving (Show)
instance RuleSet Bus where
  getRules (Bus rules) = rules

data Net = Net Bus [Rule] deriving (Show)
instance RuleSet Net where
  getRules (Net bus rules) = getRules(bus) ++ rules


bus = Bus [Rule "Rule 1", Rule "Rule 2"]
net = Net bus [Rule "Own net rule"]
main = putStrLn(show $ getRules(net))